It is conventionally known to use a foil bearing as a bearing for a rotating member that rotates at a high speed from tens to hundreds of thousands rpm, in which the foil bearing comprises a plurality of foils for forming a bearing surface. As the rotating member rotates, a fluid is dragged in between a journal (or shaft) of the rotating member and the foils, and due to the resulting fluid pressure, the foils are deformed and a fluid membrane is formed in the gap between the journal and the foils.
Some of such foil bearings comprise a stationary mount member surrounding an outer circumferential surface of the journal via an annular gap and a foil assembly disposed inside the stationary mount member to support the journal, wherein the foil assembly may be constituted by wave-shaped bump foils, an annular mid foil, and an annular top foil which are radially placed in this order from outside to inside within the stationary mount member. In order to achieve a desired bearing performance, it is necessary to position and secure each foil accurately with respect to the stationary mount member.
An example of a technique to secure the foils to the stationary mount member is disclosed in U.S. Pat. No. 7,070,330 issued to Agrawal. The foil bearing disclosed in this publication comprises first and second foil elements (top foil and mid foil) whose ends are bonded to each other to form a radially extending anti-rotation fin, and a corrugated resilient backing member (bump foil) including a flange portion projecting in the radial direction, wherein the anti-rotation fin and the flange portion are disposed in a slot formed in the stationary retaining (mount) member.
In the conventional technique disclosed in the above publication, the disposing of the anti-rotation fin and flange portion in the slot may restrain the foils against rotation. However, there is no consideration given in this publication to ensure accurate positioning of each corrugation of the resilient backing member in a circumferential direction. Also, the provision of slot in the stationary mount member can necessitate additional steps in manufacturing the stationary mount member and/or reduce the mechanical strength of the stationary mount member.
Further, in a case that the foil bearing comprises a plurality of bump foils arranged in the circumferential direction and welded to the inner circumferential surface of the stationary mount member, it is difficult to utilize the conventional technique disclosed in the above publication and a skilled person is needed to position the bump foils accurately with respect to the stationary mount member or at desired circumferential positions and secure them to the stationary mount member.